In a photoemission experiment, the maximum kinetic energies of photoelectrons from metals P , Q and R are E P , E Q and E R , respectively, and they are related by E P = 2 E Q = 2 E R . In this experi

Question

In a photoemission experiment, the maximum kinetic energies of photoelectrons from metals P , Q and R are E P , E Q and E R , respectively, and they are related by E P = 2 E Q = 2 E R . In this experiment, the same source of monochromatic light is used for metals P and Q while a different source of monochromatic light is used for the metal R . The work functions for metals P , Q and R are 4 . 0 eV , 4 . 5 eV and 5 . 5 eV , respectively. The energy of the incident photon used for metal R , in e V is ___.

TestHub · Accepted Answer

Let the maximum kinetic energies of photoelectrons be $E_{P} = 2 E_{Q} = 2 E_{R} = 2 E$ .

The energy of incident photon on metal $P and Q$ be $U$ and for $R$ be $U'$ .

Photoelectric equation, $E_{ph} = ϕ + K E_{\max}$

Now, using it for the three cases,

$U = 4 + 2 E . . . (1) U = 4.5 + E . . . (2) U' = 5.5 + E . . . (3)$

From $(1) and (2)$ , $E = 0.5 eV$

From $(3)$ , energy of the incident photon for metal $R$ ,

$U' = 5.5 + 0.5 = 6 eV$

Physics - Modern Physics Question with Solution | TestHub

Doubts & Discussion